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1 | package DBIx::Class::Storage::DBI::Replicated::Balancer::Random; |
2 | |
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3 | use Moose; |
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4 | with 'DBIx::Class::Storage::DBI::Replicated::Balancer'; |
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5 | use DBIx::Class::Storage::DBI::Replicated::Types 'Weight'; |
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6 | use namespace::clean -except => 'meta'; |
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7 | |
8 | =head1 NAME |
9 | |
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10 | DBIx::Class::Storage::DBI::Replicated::Balancer::Random - A 'random' Balancer |
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11 | |
12 | =head1 SYNOPSIS |
13 | |
14 | This class is used internally by L<DBIx::Class::Storage::DBI::Replicated>. You |
15 | shouldn't need to create instances of this class. |
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16 | |
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17 | =head1 DESCRIPTION |
18 | |
19 | Given a pool (L<DBIx::Class::Storage::DBI::Replicated::Pool>) of replicated |
20 | database's (L<DBIx::Class::Storage::DBI::Replicated::Replicant>), defines a |
21 | method by which query load can be spread out across each replicant in the pool. |
22 | |
23 | This Balancer uses L<List::Util> keyword 'shuffle' to randomly pick an active |
24 | replicant from the associated pool. This may or may not be random enough for |
25 | you, patches welcome. |
26 | |
27 | =head1 ATTRIBUTES |
28 | |
29 | This class defines the following attributes. |
30 | |
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31 | =head2 master_read_weight |
32 | |
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33 | A number greater than 0 that specifies what weight to give the master when |
34 | choosing which backend to execute a read query on. A value of 0, which is the |
35 | default, does no reads from master, while a value of 1 gives it the same |
36 | priority as any single replicant. |
37 | |
38 | For example: if you have 2 replicants, and a L</master_read_weight> of C<0.5>, |
39 | the chance of reading from master will be C<20%>. |
40 | |
41 | You can set it to a value higher than 1, making master have higher weight than |
42 | any single replicant, if for example you have a very powerful master. |
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43 | |
44 | =cut |
45 | |
46 | has master_read_weight => (is => 'rw', isa => Weight, default => sub { 0 }); |
47 | |
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48 | =head1 METHODS |
49 | |
50 | This class defines the following methods. |
51 | |
52 | =head2 next_storage |
53 | |
54 | Returns an active replicant at random. Please note that due to the nature of |
55 | the word 'random' this means it's possible for a particular active replicant to |
56 | be requested several times in a row. |
57 | |
58 | =cut |
59 | |
60 | sub next_storage { |
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61 | my $self = shift @_; |
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62 | |
63 | my @replicants = $self->pool->active_replicants; |
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64 | |
65 | if (not @replicants) { |
66 | # will fall back to master anyway |
67 | return; |
68 | } |
69 | |
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70 | my $master = $self->master; |
71 | |
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72 | my $rnd = $self->_random_number(@replicants + $self->master_read_weight); |
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73 | |
74 | return $rnd >= @replicants ? $master : $replicants[int $rnd]; |
75 | } |
76 | |
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77 | sub _random_number { |
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78 | rand($_[1]) |
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79 | } |
80 | |
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81 | =head1 AUTHOR |
82 | |
83 | John Napiorkowski <john.napiorkowski@takkle.com> |
84 | |
85 | =head1 LICENSE |
86 | |
87 | You may distribute this code under the same terms as Perl itself. |
88 | |
89 | =cut |
90 | |
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91 | __PACKAGE__->meta->make_immutable; |
92 | |
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93 | 1; |